Funding:SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.This talk discusses the performance of the devices for higher than two dimensional emittance measurements, allowing studies of coupling between all transverse phase space planes, and in a more advanced set up, coupling to the longitudinal plane as well. The results of the actual phase space distribution (and not only RMS values) are very important for modeling the beam dynamics for high current operation of LINACs. Furthermore an outlook of related methods for electron beams is given.

LHC Online Chromaticity Measurement - Experience After One Year of Operation

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K. Fuchsberger, G.H. Hemelsoet
CERN, Geneva, Switzerland

Hardware and infrastructural requirements to measure chromaticity in the LHC were available since the beginning. However, the calculation of the chromaticity was mostly made offline. This gap was closed in 2015 by the development of a dedicated application for the LHC control room, which takes the measured data and produces estimates for the chromaticity values immediately online and allows to correct chroma and tune accordingly. This tool proved to be essential during commissioning as well as during every injection-phase of the LHC. It became particularly important during the intensity ramp-up with 25ns where good control of the chromaticity became crucial at injection. This paper describes the concepts and algorithms behind this tool, the experience gained as well as further plans for improvements.

Using bunch shape monitors (BSMs), we measured the longitudinal bunch lengths of negative hydrogen ion beams in the J-PARC linac. A BSM was installed between two linacs, separate-type drift tube linac (SDTL) and an annular-ring-coupled structure linac (ACS), having acceleration frequencies of 324 and 972 MHz, respectively. We used radio-frequency amplitude modulation of bunches in the beam transport between the SDTL and ACS to minimize emittance growth and beam loss. We conducted amplitude scanning and compared the results with the twiss-parameters obtained from the transverse profiles. In this paper, we discuss the results of amplitude tuning of the buncher cavity at the point of beam loss and emittance. We also discuss the measurement results for various equipartitioning settings of quadrupole magnets.

Funding:ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.Absolute measurement of vane voltage is essential to understand RFQ transmission. We used a non-intrusive technique of bremsstrahlung X-ray measurement. Several windows were installed at SNS to allow measurement of the X-ray spectrum in different locations of the RFQ. A CdTe spectrometer was used to estimate spectrum cutoff energy that corresponds to the vane voltage. Different device setups are described as well as measurement accuracy and interpretation of experimental data.

Emittance control is important for polarization preservation of proton beam in the Alternative Gradient Synchrotron (AGS). For polarization preservation, two helical dipole partial snake magnets are inserted into the AGS lattice. In addition, the vertical tune has to run very high, in the vicinity of integer. These helical dipole magnets greatly distort the optics, especially near injection. The beta functions along the energy ramp have been modeled and measured at the locations of the Ion Profile Monitor (IPM). For the measurements to be valid, the betatron tune, dipole current and orbit responses have to be carefully measured. This paper summarize the experiment results and comparison with the model. These results will lead to understanding of emittance evolution in the AGS.

The field of particle acceleration in plasma wakes has seen remarkable progress in recent years. These days, acceleration gradients in excess of 10 GV/m can be readily achieved using either ultra-short intense laser pulses or particle beams as wake drivers. With the advent of first multi-GeV electron beams from plasma and a general trend towards improved reproducibility, beam quality and control over the involved processes, plasma-acceleration techniques are starting to draw considerable interest in the traditional accelerator community. Part of this attention is based on the extreme beam properties obtainable with plasma, such as femtosecond duration and sub-micron normalized transverse emittance, which pose significant obstacles for beam characterization and require cutting-edge detection concepts. In addition, the conservation of these characteristics during beam transport is complicated by ~mm beta functions at the plasma exit in combination with correlated energy spreads typically on a percent level. This presentation will give an introduction into the field of plasma wakefield acceleration and provide an overview about challenges in diagnosing the generated beams.

Beam instrumentation systems at CERN require periodic verifications of both their state and condition. Presently, experts have no generic solution to observe and analyse an instrument's condition and as a result, many ad-hoc Python scripts have been developed to extract historical data from CERN's logging service. Clearly, ad-hoc developments are not desirable for medium/long term maintenance reasons and therefore a generic solution has been developed. In this paper we present the Offline Analysis Framework (OAF), used for automatic report generation based on data from the central logging service. OAF is a Java / Python based tool which allows generic analysis of any instrument's data extracted from the database. In addition to the generic analysis, advanced analysis can also be performed by providing custom Python code. This paper will explain the steps of the analysis, its scope and present the kind of reports that are generated and how instrumentation experts can benefit from it. We will also show how this approach simplifies debugging, allows code re-use and optimises database and CPU resource usage.

The LHC Schottky monitors have the potential to measure and monitor some important beam parameters, tune, momentum spread, chromaticity and emittance, in a non-invasive way. We present recent upgrade and improvement efforts of the transverse LHC Schottky systems operating at 4.8 GHz. This includes optimization of the slotted waveguide pickups and a re-design of the RF front-end electronics to detect the weak, incoherent Schottky signals in presence of large, coherent beam harmonics.

Funding:Work supported the URA., Inc., under contract DE-AC02-76CH03000 with the U.S. Dept. of EnergyWe review tests of the head-tail phase shift method using various approaches at BNL's RHIC. Both the standard and some more exotic approaches to measure the phase differential between the head and tail of a bunched beam has been attempted at RHIC. The standard kick beam and measured phase evolution of the head and tail of a given bunch has been tried at RHIC. Additionally a more exotic approach to measure the head versus tail phase difference has been tried. In this approach we used a BBQ pickup and kicker with the input stripline signal to the BBQ mixed with a nano second pulse timed to the head and tail of the bunch. In this way we hoped to force the BBQ to sample the head or tail of the bunch depending on the pulse timing. We report on the results and challenges which each approach presented.

This presentation will review the performance and limitations of present beam instrumentation in relation to beam dynamics studies, and give an overview of the main requirements from the accelerator physics community for new or improved measurements that need R&D effort from the beam diagnostics side.

The use of the Metrology Light Source (MLS), the electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB, the German national metrology institute) as a primary radiation source standard requires the accurate measurement of all storage ring parameters needed for the calculation of the spectral radiant intensity of the synchrotron radiation. Therefore, instrumentation has been installed in the MLS for the measurement of, e.g., the electron beam energy, the electron beam current or the electron beam size that outperforms that usually installed in electron storage rings used as a common synchrotron radiation source. We report on the status and improvements in the storage ring parameter measurement.

Funding:Work supported by MEXT KAKENHI, GA 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled "Unification and Development of the Neutrino Science Frontier"In high intensity proton synchrotrons, linear and nonlinear betatron resonances cause beam loss. When the betatron tune spreads over a resonance line, the oscillation amplitude will get larger, causing a large beam loss. Our study aims for a direct measurement of the betatron tune spread by using a quadrupole kicker and a 4-electrode monitor. The monochromatic rf signal is inputted to the kicker and we induce an oscillation by kicking the beam. The amplitude of the quadrupole oscillation will depend on the number of particles having a certain tune. In the beam test at J-PARC MR, the dipole kicker was used as a quadrupole kicker by exciting the two facing electrodes in-phase. We measured the response to the kick at several frequencies. We observed that the amplitude depends on the kicker frequency and the number of particles per bunch. This demonstrates that the quadrupole oscillation can be induced by a kicker and the possibility of measuring the number of a particular tune particle from the response. We will present the result of the beam test and our prospect and the comparison between the experimental result and a numerical calculation.

Longitudinal coupling impedances can be deduced from S-Parameter measurements performed on a Goubau Line. The Goubau Line, also known as single wire line, is a variant of the coaxial wire method. Both setups use a wire for mimicking the particle beam. Coaxial tapers at the wire ends adapt wave impedance to the 50ohm impedance of coaxial cables, sources and receivers. But for guiding the electromagnetic wave, the Goubau Line relies on the realistic boundary conditions imposed by an insulated wire instead of using a coaxial shield. Equations for the deduction of longitudinal coupling impedances are reviewed and applied to Goubau Line measurements. Goubau Line measurements and CST Studio simulations are compared, showing good agreement.

A new step of the SPIRAL2 commissioning started in December 2015 with the acceleration of a first proton beam at the RFQ exit. A test bench, with all the different diagnostics which will be used on the SPIRAL2 accelerator, was installed directly after the first rebuncher of the MEBT line in order to qualify beams but also to test and make reliable the diagnostic monitors. In 2016, different ion beams are qualified by the diagnostic test bench. This paper describes the results of the energy measurements done by a Time of Flight monitor and the longitudinal measurements using a fast faraday cup.

At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design is that the corrector magnets all have the same dynamic response. In this paper, a procedure to measure the frequency responses of the corrector magnets on the Diamond Storage Ring is presented and the magnet responses are measured and compared in order to assess whether this assumption is valid. The measurements are made by exciting a single corrector magnet with a sinusoidal input and measuring the resulting sinusoidal movement on the electron beam using electron Beam Position Monitors (eBPMs). The input excitation is varied from 10 Hz to 5 kHz using a 10 mA sine wave. The amplitude ratio and the phase difference between the input excitation and the beam position excitation are determined for each input frequency and the procedure is repeated for several magnets. Variations in both gain and phase across magnets are discussed in this paper and the effect of such variations on the performance of the FOFB controller performance is determined.

Virtual bunch length measurement can be carried out by means of ELEGANT code for tracking the bunch particles from RF deflector to the screen. The technique relies on the correlation between the bunch longitudinal coordinate and transverse coordinates induced through a RF deflector. Therefore, the bunch length measurement can be carried out measuring the vertical spot size at the screen, placed after the RF deflector. The deflecting voltage amplitude affects the resolution. Adding a dispersive element, e.g. a magnetic dipole between RF deflector and the screen, the full longitudinal phase space can be measured. In this paper, we discuss some issues relevant for the electron linac of the Compton source at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP).

Corrugated structures have recently been widely used for manipulating electron beam longitudinal phase space and for producing THz radiation. Here we report on time-resolved measurements of the quadrupole wakefields in planar corrugated structures. It is shown that while the time-dependent quadrupole wakefield produced by a planar corrugated structure causes significant growth in beam transverse emittance, it can be effectively canceled with a second corrugated structure with orthogonal orientation. The strengths of the time-dependent quadrupole wakefields for various corrugated structure gaps are also measured and found to be in good agreement with theories. Our work should forward the applications of corrugated structures in many accelerator based scientific facilities.